The present invention relates to a liquid crystal apparatus and more particularly, to a liquid crystal apparatus having a liquid crystal layer comprising a polymer dispersed in a liquid crystal molecule.
A reflection type liquid crystal display unit has conventionally a configuration in which a liquid crystal panel is arranged between a pair of polarization plates and reflector is arranged on one of substrates. However, because of the necessity of using a polarization plate, the conventional reflection type liquid crystal display unit suffers much loss of light, resulting in a very dark display.
There is available, on the other hand, a polymer dispersion type liquid crystal display unit having a liquid crystal layer comprising a liquid crystal molecule and a polymer, as a liquid crystal apparatus of a type not using a polarization plate. This polymer dispersion type liquid crystal display unit performs display by the utilization of a light transmission state and a light scattering state. When mixing a dichroic dye in the liquid crystal layer of such a polymer dispersion type liquid crystal display unit, display is accomplished by a light absorbing state and a light scattering state.
The liquid crystal display unit of such a configuration has however a problem in that light absorption by the dichroic is insufficient in the voltage non-applied state.
In a liquid crystal display unit of the polymer dispersion type, in which a xc2xc wavelength plate and a reflector is arranged on the outside of one of substrates, the light passes therethrough in the following sequence.
After the light having entered the liquid crystal display unit from outside passes through one of the substrates, the light passes through the liquid crystal layer. Then, after passing through the other substrate, the light passes through the xc2xc wavelength plate and is reflected on the reflector. The reflected light passes again through the xc2xc wavelength plate, passes sequentially through the other substrate, the liquid crystal layer and the first substrate, and is emitted outside the liquid crystal apparatus. This conventional polymer dispersion type liquid crystal display unit has a problem in that, because of a distance between an electrode formed within the substrate and the reflector formed on the outside of the substrate, a parallax is present in a display of the liquid crystal display unit.
A main object of the present invention is to provide a liquid crystal apparatus of a high contrast rates, which improves parallax in the liquid crystal apparatus and gives a higher light absorption caused by a dichroic dye.
In a preferred embodiment of the liquid crystal apparatus of the invention:
a liquid crystal layer comprises a liquid crystal molecule, a polymer an a dichroic dye and held between a pair of substrates; a reflection layer is formed on one of the substrates on one of the substrates on the such having the liquid crystal layer formed thereon; and a retardation film is formed on the reflection layer.
This configuration makes it possible to obtain a light absorbing state by the dichroic dye upon non-application of voltage, and a light scattering state upon application of voltage. The retardation film (xc2xc wavelength layer) formed in the liquid crystal apparatus converts the light reflected on the reflector into a light having a polarization component in a prescribed direction. The light is therefore absorbed by the dichroic dye contained in the liquid crystal layer through which the light passes again. In addition, also upon application of voltage, the light reflected on the reflector is converted into a light having a prescribed direction by the retardation film, and scattered in the liquid crystal layer through which it passes again. More specifically, the light can be scattered due to the difference in refractive index between the liquid crystal molecule and the polymer.
It is therefore possible to increase the extent of absorption in the light absorption state, and at the same time, to increase the degree of light scattering in the light scattering state. There is thus available a liquid crystal apparatus having an improved contrast.
Under the effect of the configuration in which an electrode is formed on the retardation film and another electrode is formed on the other substrate, there is available, upon non-application of voltage, the light absorption state of the liquid crystal apparatus by the arrangement of the liquid crystal molecule, the polymer and the dichroic dye in substantially the same direction. Upon application of voltage, the liquid crystal molecule and the dichroic dye are arranged in the electric field direction, thus making it possible to obtain a light scattering state of the liquid crystal apparatus.
In a preferred embodiment of the liquid crystal apparatus of the invention:
a liquid crystal layer comprising a liquid crystal molecule, a polymer and a dichroic dye in held between a pair of substrates; a reflecting layer is formed on a substrate on the side having the liquid crystal layer formed thereon; a retardation film is formed on the reflecting layer; and an electrode is formed on the retardation film.
This configuration makes it available a light absorption state by the dichroic dye upon non-application of voltage, and a light scattering state upon application of voltage.
Further, arrangement of the retardation film (xc2xc wavelength layer) permits conversion of the light reflected on the reflecting layer into a light having a prescribed polarization component. Upon non-application of voltage, the light is absorbed by the dichroic dye, and upon application of voltage, it is possible to increase the contrast ratio between voltage non-application and application states.
The configuration, in which a pixel electrode is formed in a matrix shape on the retardation film, and a switching element connected to the pixel electrode is formed, makes it available a liquid crystal apparatus of a clear image display because of the possibility of controlling the state of the liquid crystal for each picture element.
It is possible to adopt a configuration in which an optical isotropic layer not producing an optical action is formed between the retardation film and the liquid crystal layer. It is also possible to obtain a liquid crystal apparatus capable of color display in a configuration in which a color filter comprising a plurality of color elements is formed on the other substrate at a position opposite to the pixel electrode. A color filter having red, blue and green color elements or a color filter having yellow, magenta and cyan color elements may be used, and a clear image display is available.
In a preferred embodiment of the liquid crystal apparatus of the invention:
a liquid crystal layer comprising a liquid crystal molecule, a polymer and a dichroic dye is held between a pair of substrates; an electrode having a reflecting property is formed on one of substrates on the side having the liquid crystal layer formed thereon; and a retardation film is formed on the electrode.
In this configuration, it is possible to form the electrode directly on the substrate, and to simplify the manufacturing process without the necessity to separately form the reflecting film and the electrode. Upon non-application of voltage, a light absorbing state is obtained from the dichroic dye, and upon application of voltage, there is available a light scattering state. Further, by providing a retardation film (xc2xc wavelength layer), it is possible to convert the light reflected on the reflecting layer into a light having a prescribed polarization component. Therefore, upon non-application of voltage, the light is absorbed by the dichroic dye, and upon application of voltage, the light is scattered, thus enabling to increase the contrast ratio between non-application and application of voltage.
By using a configuration in which the electrode comprises a plurality of pixel electrodes arranged in a matrix shape, and switching elements connected to the pixel electrodes are formed, it is possible to control voltage to be applied onto the liquid crystal for each picture element and to control the state of the liquid crystal layer for each picture element, thus permitting obtaining a liquid crystal apparatus displaying a high-quality image. It is also applicable as a light valve.
By adopting a configuration in which a color filter comprising a plurality of color elements is formed on the other substrate, there is available a liquid crystal apparatus capable of performing color display.
In a preferred embodiment of the liquid crystal apparatus of the invention:
pixel electrodes formed into a matrix shape and switching elements connected to the pixel electrodes are formed on the substrate on the light incidence side; a reflecting layer and a retardation film are formed on the substrate opposite thereto; and the liquid crystal layer comprises a liquid crystal, a polymer and a dichroic dye. A highly accurate liquid crystal apparatus is available also with this configuration.
Since the present invention covers a reflection type liquid crystal apparatus which does not require use of a light source (known as a back light), liquid crystal apparatus of a low power consumption is available. Further, because this is a liquid crystal apparatus of a mode not requiring the use of a polarization plate, a liquid crystal apparatus of a bright display is obtained.
By mounting a liquid crystal apparatus having any of the foregoing configurations on an electronic equipment, it is possible to obtain an electronic equipment of a low power consumption is available, and this is particularly useful for a portable electronic equipment.
For example, it is possible to mount the liquid crystal apparatus as a light valve, and mount the same as a display unit of the invention onto the display section of a portable electronic equipment.